Sound reproducing device



Aug. 17, 1937. .1. B. BRENNAN SOUND REPRODUCING DEVICE Filed March 27,1933 Patented Aug. 17, 1937 UNITED STATES PATENT OFFICE Claims.

The present invention relates to a sound-reproducing device utilizing adiaphragm of a comparatively wide range of movement or amplitude with amoving coil connected thereto for driving 5 the diaphragm so that whenvoice currents pass therethrough the coil will move transversely ofmagnetic lines in one direction and when the direction of current isreversed the movement of the coil will be reversed, the driving coilbeing disposed between inner and outer magnetic pole pieces within avery narrow air gap.

In such devices it is important that the coil be positioned in such anarrow air gap with but a slight clearance and yet so mounted as topermit a wide range of movement or amplitude while at the same time beproperly centered throughout its wide range of movement.

Therefore, the present invention is to provide in combination with suchdevices a coil-centering diaphragm or supporting disc so designed andconstructed as to permit a wide range of movement or amplitude of thedriving coil in the narrow air gap but which will at the same timeproperly center the coil against transverse movement in the gapthroughout its wide range of amplitude.

A further object of the invention is the provision of a novel type offlexible disc for accurately centering the movable coil in the air gap.

A still further object of the invention is the provision of novel formof centering device or disc or washer constructed of corrugatedyieldable material. These corrugations may be concentric or in variousother forms whereby to increase the flexibility of the washerlongitudinally of the coil without unduly reducing or decreasing thelateral stiffness or rigidity. Thus the cone diaphragm may be vibratedfreely and at the same time the coil will be accurately centered.

Further objects of the invention are to provide a construction ofmaximum simplicity, economy and ease of assembly and such furtherobjects, advantages and capabilities as will later more fully appear andare inherently possessed thereby.

The invention further resides in the combination, construction andarrangements of parts 11- lustrated in the accompanying drawing, andwhile there is shown therein a preferred embodiment, it is to beunderstood that the same is susceptible of modification and change, andcomprehends other details, arrangements of parts, features andconstructions, without departing from the spirit of the invention.

Referring to the drawing:

Fig. 1 is a longitudinal central section of aloud speaker;

Fig. 2 is a plan view of the novel washer or centering member;

Fig. 3 is a cross sectional view of Fig. 2 taken 00 on the line 3-3 ofFig. 2;

(Cl. PIS-115.5)

Fig. 4 is a plan view of an alternate construction of centering memberprovided with spiral corrugations;

Fig. 5 is a fragmentary vertical cross sectional view of a furthermodification of centering 5 member;

Fig. 6 is a fragmentary vertical cross sectional view of anotheralternate construction.

Referring more particularly tothe disclosure in the drawing, theembodiment selected to illus- 10 trate the invention comprises anelectro-magnet having a fleldcoil I provided with a core 2, and polepiece 3 provided with an opening 4 to receive the core 2. A centeringplate 5 encompasses the core 2 and is suitably connected to the polepiece 3 by means of studs 6 whereby to maintain the pole piece incentered position. The electro-magnet is housed within the casing orhousing I.

Mounted within the casing or pan 8 is a dia- 20 phragm 9. This diaphragmis shown in the form of a cone having its outer periphery or flange l0flexibly seated intermediate annular members are rings ll mounted in theouter edge or periphery i2 01' the pan. This pan is suitably secured to25 the magnet 3 by means of studs 03.

The reduced or inwardly extending portion of the pan forms an annularsupport 14 to which is connected the flexible disc or coil-centeringdiaphragm l5 as by means of bolts or other suit- 30 able retaining meansIS. The interior portion of this coil-centering diaphragm is bentupwardly or outwardly to form an annular flange or collar I! forreceiving a coil-supporting cylinder 18. This cylinder is provided witha reduced portion 35 19 upon which is mounted a driving coil 20.

The cylinder l8 at its outer end is adapted to receive a reduced flangeor collar 2| of the cone or diaphragm 9. Any suitable attaching meanssuch as cement or the like may be employed in 40 connecting the flange2|, cylinder I8, and the flange l1 0! the coil-centering means or discI5 together, so that these members may move as a unit.

As clearly disclosed in Fig. 1, the coil 20 is 45 disposed in the airgap between the core and pole piece of the magnet. In order that thistype of speaker may operate efficiently, it is desirable that the airgap 4 between the core and pole piece be reduced to a minimum and that50 the coil 20 be accurately centered with respect to said core, whileat the same time permitting a wide range of longitudinal movement of thecoil 20. In order to permit such wide range of amplitude and at the sametime prevent any 55 transverse movement of the coil in such air gap, Ihave provided the disc or coil-centering means l5. In its preferredform, this disc or centering device is made of a thin flexible materialsuch as parchment, glazed paper or other material or fabric which hasbeen provided with corrugations. It is also highly desirable that thismaterial be non-hydroscopic.

Various forms of corrugations may be provided as disclosed in theseveral figures. In Figures 1, 2, and 3, such corrugations 22 are shownas concentric, while in Fig. 4 the corrugations 23 are shown as spiral.In Fig. 5, the angular corrugations 24' may be either concentric orspiral, while in Fig. 6 the corrugations 25 are shown in the form ofoverlapping or superimposed folds or corrugations rather than asradially or concentric corrugations as in the previous figures.

. However, it is to be understood that since the purpose of thesecorrugations is to increase the flexibility of the coil-centering memberor disc longitudinally without unduly reducing the lateral stifiness orrigidity thereof, various forms or shapes of corrugations or the likemay be provided for effecting the desired results.

In the figures, the disc or coil-centering member is disclosed as ofsubstantial thickness, although it is to be understood that thisthickness in the disclosure is exaggerated and that the washer, disc orcentering means is formed of a thin, non-porous material. By reason ofthe flexibility of this coil-centering means or disc, the driving coil20 for the cone diaphragm has a free and wide range of movementlongitudinally in the air gap, while at the same time, it is preventedfrom' moving transversely within such gap. These corrugations alsoincrease the life of the coil-centering disc or diaphragm since it maybe subjected to a much wider range of vibration and for a much greaterperiod of time without damage thereto.

Having thus disclosed the invention,

I claim:

1. In an apparatus for sound reproduction, a diaphragm flexiblysupported at its base, a coil supporting portion connected therewith, anactuating coil mounted on the coil supporting portion, and acoil-centering member engaging the coil supporting portion and providedwith corrugations of approximately uniform diameter arranged concentricwith the axis of the coil for permitting free longitudinal movement ofsaid coil in such manner as to permit a wide range of movement of thecoil while at the same time preventing lateral movement thereof.

2. In an apparatus for sound reproduction, a diaphragm flexiblysupported at its base, a coilsupporting portion connected therewith, anactuating coil mounted on the coil-supporting portion, and acoil-centering member engaging the coil-supporting portion and providedwith overlapping folds of uniform diameter concentric with the axis ofthe coil for permitting free longitudinal movement of the coil-centeringmember and coil and thereby permitting a wide range of I movement of theactuating coil while maintaining said coil centered.

3. In an apparatus for sound reproduction, a diaphragm flexiblysupported at its base for free longitudinal movement, a coil-supportingportion secured to said diaphragm, an actuating coil mounted on thecoil-supporting portion and adapted to receive the voice currents, and amember constructed of flexible material with axially spaced corrugationsconnected with the coilsupporting portion in such manner as to permitfree longitudinal movement of said member and coil and a wide range ofamplitude of the coil, but possessing sumcient stifiness to center thecoil and prevent lateral movement thereof.

4. In a sound producing device having an acoustical diaphragm flexiblysupported at its base, and a wound actuating coil secured thereto, acoil-centering member having a circular portion at its outer edge forsecuringthe said member in place in the sound producing device, saidcoilcentering member being provided with a coaxial flange adapted tosupport and center the actuating coil and a relatively deep wellconcentric with said flange, substantially as and for the purpose setforth.

5. In a sound producing device having a hollow acoustical diaphragm anda wound actuating coil therefor, a coil-centering member having asupported portion at its outer periphery adapted to be supported in thesound producing device, a central flange-like supporting portion adaptedto support and center an actuating coil, a relatively deep wellconcentric with and adapted to surround the supporting coil, andcorrugations interposed in the coil-centering member between thesupported and flange like supporting portions.

JOSEPH B. BRENNAN.

